A showdown pitting human brains against artificial intelligence goes ahead this evening when two professional poker players take on a computer in the world's first such man-machine challenge. Phil Laak and Ali Eslami will play Polaris, the most sophisticated poker-playing program yet written, the product of years of research and refinement by a team of artificial intelligence experts at the University of Alberta in Canada.

The challenge will play out over two days and 500 hands of Texas hold 'em at the Hyatt Regency hotel in Vancouver, with the players gambling for a total prize pot of $50,000 (Â£23,000). Jonathan Schaeffer, the lead scientist behind Polaris, said that, even though his program had the perfect poker face, it was not the favourite to win. Nevertheless, he promised to make his opponents work for their prize money. "I'm not nervous," he said. "Everyone expects the humans to win."

Last week, Dr Schaeffer published details of an artificial intelligence draughts-playing game that cannot be beaten.